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Heat Budget of Earth, Meaning, Diagram, Significance

Heat Budget of Earth

A heat budget is a precise balance between the heat that the earth radiates away from the sun and the heat that it collects from the sun (Insolation or terrestrial radiation).

Earth would be getting either too warm or too cold if the balance between incoming and existing heat were off. These variables are properly balanced, which results in the perfect temperature of the earth. The equilibrium between insolation (short waves) and terrestrial radiation is known as the Earth’s Heat Budget (long waves).

Read More: Heat Transfer Methods

Heat Budget of Earth Atmosphere

Depending on its location, the Earth’s surface receives different amounts of solar radiation, with some areas receiving more than others. Between 40°N and 40°S, there is a surplus of net radiation balance, whereas there is a deficit in the areas close to the poles.

The poles receive a redistribution of the extra heat energy from the tropics. This balance is absolutely essential because it prevents the tropics from becoming extremely hot from the buildup of excess heat and prevents locations at high altitudes from becoming permanently frozen from a lack of radiation.

Read More: Isotherms

Heat Budget of Earth in Detail

The concept of a heat budget is related to how much solar heat energy is collected and utilised both on the surface of the earth and in the atmosphere. The average temperature of the Earth overall does not change despite the continuous supply of sun rays. This is only possible if the Earth’s system sends an equal quantity of energy back into space. There is a balance or equilibrium between incoming solar radiation & outgoing terrestrial radiation. This balance is known as the Heat Budget of Earth.

Let’s consider that the insolation received at the top of the atmosphere is 100 per cent. While passing through the atmosphere, some amount of energy is reflected, scattered, and absorbed. Only the remaining part reaches the Earth’s surface. Even before they reach the surface of the Earth, around 35 units are reflected back to space. The detailed break-up of this reflected radiation is as under:

  • From the top of clouds, Reflected Radiations – 27 units
  • By ice fields on earth, Reflected Radiations – 02 units
  • Reflected by the atmosphere – 06 units
  • Total – 35 units

Albedo of the Earth

The reflected amount of radiation has referred to the albedo of the Earth. Thus, this 35 per cent of radiation neither heats the atmosphere nor the Earth’s surface. The remaining 65 units are absorbed as:

  • Absorbed by the atmosphere – 14 units
  • Absorbed by the earth – 51 units (Scattered + direct radiation)
  • Total – 65 units

Gas molecules and dust particles cause scattering. This occurs in all directions, with part of it moving towards the planet and some toward space. Overall, the earth receives 51 units of radiation, which radiates back in the form of terrestrial radiation. The details about this reflected radiation are as described in the following:

  • Radiated to space directly – 17 units
  • Radiated to the atmosphere – 34 units

The details of 34 units of radiation absorbed by the atmosphere from terrestrial radiation are:

  • Absorbed directly – 06 units
  • Absorbed through convection and turbulence – 09 units
  • Absorbed through Latent heat of condensation5 – 19 units; (Latent heat refers to the energy released or absorbed by a body)
  • Total – 34 units

The total units absorbed by the atmosphere are 48 (14 units of insolation + 34 units of Terrestrial radiation). These are radiated back into space. Thus, the total radiation returning from the earth and the atmosphere respectively are:

  • Radiated back by earth – 17 units
  • Radiated back by the atmosphere – 48 units
  • Total – 65 units

These returning 65 units balance the total of 65 units received from the sun. This account of incoming and outgoing radiation always maintains the balance of heat on the earth’s surface. This is known as the heat budget of earth or heat balance of the earth.

Read More: Temperature Inversion

Heat Budget of Earth Diagram

The world maintains a constant temperature through this exchange of heat, and this phenomenon is known as the earth’s heat budget. Here is the diagram of the Heat Budget.

Heat Budget of Earth
Heat Budget of Earth

Read More: Heat Zones of Earth

Latitudinal Heat Balance

Although the whole earth maintains a balance between the incoming and the outgoing radiation of the earth, this is not true when we look at different latitudes. At the latitudinal level, the heat budget is not zero. As discussed earlier, the insolation obtained is directly related to latitudes. One part of the world has a surplus radiation balance, and the other part is lacking. There is a surplus of radiation balance between 40 degrees N&S and the regions near the poles are in short supply. This, in theory, should mean that the tropics should gradually warm up and that the Arctic and Antarctic become even cooler. But that is not the case. The excess heat energy from the tropics is redistributed towards the poles by ocean currents, wind flow, air circulation etc.

As a result, the tropics neither heat up continuously due to excessive heat accumulation, nor the polar latitudes are permanently under snow due to extreme shortages. According to some estimates, about 75 per cent of the heat is transferred through atmospheric circulation and the remaining 25 per cent is transferred by oceanic circulations. Winds and currents in the oceans are produced due to thermal imbalances.

Read More:  List of Major Local Winds

Heat Budget of Earth UPSC

The sun is the most powerful heat generator. And the primary cause of all climatic traits is the varied amounts of heat that different parts of the globe receive from the sun. In order to comprehend various climatic elements like wind systems, pressure systems, precipitation, etc., it is vital to understand the patterns of temperature distribution in different seasons. A crucial component of your UPSC preparation is geography. Both the UPSC Prelims and Mains General Studies Paper I include it. You may study everything about Heat Budget for the IAS Exam in this post.

Other Indian Geography Topics

Seasons of India Mountains of India
Mangrove Forests in India Important Mountain Passes in India
Monsoon in India
Indus River System
Climate of India
Rivers of India
Tributaries of Ganga
National Parks in India
Important Dams in India
Wildlife Sanctuaries of India
Tiger Reserves in India
Northern Plains of India
Physiography of India
Important Lakes of India
Wetlands in India
Biodiversity in India
Natural Vegetation in India Earthquakes in India
Types of Soil in India
Ramsar Sites in India
Brahmaputra River System
Hydropower Plants in India
Nuclear Power Plants in India
Major Ports in India
Biosphere Reserves in India
Waterfalls in India

Other Fundamental Geography Topics

Solar System Types of Clouds
Structure of the Atmosphere Himalayan Ranges
Component of Environment
El Nino and La Nina
Coral Reef
Continental Drift Theory
Endogenic and Exogenic Forces
Indian Ocean Region
Pacific Ocean
Indian Ocean Dipole
Air Pollution
Environmental Impact Assessment
Tropical Cyclone
Western Disturbances
Types of Rocks

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Why is heat budget important?

A heat budget is a perfect balance between the amount of heat that enters the planet, is absorbed by it, and leaves it as radiation. The heat budget is crucial because it clarifies why, despite the enormous heat transfer that occurs, the globe never warms or cools.

What is the global heat budget?

The equilibrium between solar radiation coming in and flowing out is known as the global heat budget. The amount of incoming solar energy changes throughout the year and for various areas throughout the world.

How is the heat budget maintained?

Using the equilibrium of solar radiation between conduction and advection.

How can heat losses be reduced?

The main defence against heat loss through floors, walls, windows, and roofs is better insulation for your home. In order to prevent heat loss, you can either add extra insulation or make sure there are no gaps in the insulation that is already there.

What is the type of heat transfer?

Three processes—radiation, conduction, and convection—are involved in the movement of heat into and through the atmosphere.


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